1. Field of the Invention
The present invention relates to an information embedding apparatus, an information embedding method, an information detecting apparatus and an information detecting method, more particularly to an information embedding apparatus and an information embedding method for adding an information to a document image by embedding the information therein, and an information detecting apparatus and an information detecting method for detecting the information embedded in and added to the document image from the printed document image.
2. Description of the Related Art
An electronic watermarking technology in which dots are printed in a documented image so that data is embedded therein has been proposed. For example, as recited in Japanese Laid-Open Patent Publication No. 2004-128845, the dots to be embedded in the document image as the electronic watermark are embedded in accordance with three different arrangement methods so that each of the embedding arrangement methods (types) has a meaning. Further, as recited in Japanese Laid-Open Patent Publication No. 2003-101762, the data is embedded in the document image depending on in which direction the dot is darker or lighter.
The technology of “electronic watermarking for document” for embedding data in a background of the document image as a ground pattern can also be applied to MFP (Multi Function Peripherals)/LBP (Laser Beam Printer). A method for embedding and detecting the data in such a manner that a resistance against a noise factor (any unnecessary dot unintentionally printed, dot resulting from a screening process and the like) can be assured was necessary in scanning the printed document in which the data is embedded as the ground pattern by a scanner so that the data is detected. Further, it was necessary that simplified processing steps which can be realized in terms of hardware constitute the detecting function in order to install the detecting function in the MFP.
However, the method recited in Japanese Laid-Open Patent Publication No. 2004-128845 is not practical in use because it fails to attain an expected resistance against the noise factor. Further, it is not possible to add such a dot that can constitute the background image of the document image because each of the different dot arrangements includes the meaning of the data.
In the method recited in Japanese Laid-Open Patent Publication No. 2003-101762, the data is embedded depending on in which direction the dot is darker or lighter in the document image, which demands a complicated processing when the embedded data is detected. Therefore, it is difficult to make the method into hardware. Further, the method fails to achieve a high-speed processing as software either since a detecting apparatus undergoes too large a load.